I wouldn't worry about getting counterfeit products from an authorized Canon dealer however many of them do sell gray market products which can sometimes be a good deal if you are willing to take the risk of having a warranty that may be nearly useless in a practical sense. At least the larger dealers make it clear which products are gray market (genuine Canon but not intended for sale in this market so they won't have Canon USA warranty coverage).
Where you do need to be careful is with some of the large online only general lines retailers (like that retail colossus with which we are all familiar). The chances of buying a counterfeit product there is much greater as is the commonly used practice of utilizing verbiage and photos that try to lead a potential buyer into believing that an OEM accessory or supply is being purchased when in fact it is an aftermarket product. Not only do they sometimes play games with look alike camera batteries but also items like memory cards which are often true counterfeits. One of the most commonly counterfeited items sold today is the lowly lithium coin cell.
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
